Proper span representation with syntax context

16 files changed, 413 insertions, 469 deletions

diff --git a/crates/base-db/src/span.rs b/crates/base-db/src/span.rs
index 1072d937a3b..acc1e5243f7 100644
--- a/crates/base-db/src/span.rs
+++ b/crates/base-db/src/span.rs
@@ -1,6 +1,7 @@
 use std::fmt;
 
 use salsa::InternId;
+use tt::SyntaxContext;
 use vfs::FileId;
 
 pub type ErasedFileAstId = la_arena::Idx<syntax::SyntaxNodePtr>;
@@ -9,10 +10,17 @@ pub type ErasedFileAstId = la_arena::Idx<syntax::SyntaxNodePtr>;
 pub const ROOT_ERASED_FILE_AST_ID: ErasedFileAstId =
     la_arena::Idx::from_raw(la_arena::RawIdx::from_u32(0));
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
-pub struct SyntaxContext;
+pub type SpanData = tt::SpanData<SpanAnchor, SyntaxContextId>;
 
-pub type SpanData = tt::SpanData<SpanAnchor>;
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct SyntaxContextId(InternId);
+crate::impl_intern_key!(SyntaxContextId);
+
+impl SyntaxContext for SyntaxContextId {
+    // FIXME: This is very much UB, salsa exposes no way to create an InternId in a const context
+    // currently (which kind of makes sense but we need it here!)
+    const DUMMY: Self = SyntaxContextId(unsafe { core::mem::transmute(1) });
+}
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 pub struct SpanAnchor {
@@ -26,7 +34,7 @@ impl fmt::Debug for SpanAnchor {
     }
 }
 
-impl tt::Span for SpanAnchor {
+impl tt::SpanAnchor for SpanAnchor {
     const DUMMY: Self = SpanAnchor { file_id: HirFileId(0), ast_id: ROOT_ERASED_FILE_AST_ID };
 }
 
diff --git a/crates/cfg/src/tests.rs b/crates/cfg/src/tests.rs
index 242929c006a..0ea176858c9 100644
--- a/crates/cfg/src/tests.rs
+++ b/crates/cfg/src/tests.rs
@@ -2,20 +2,30 @@ use arbitrary::{Arbitrary, Unstructured};
 use expect_test::{expect, Expect};
 use mbe::syntax_node_to_token_tree;
 use syntax::{ast, AstNode};
-use tt::Span;
+use tt::{SpanAnchor, SyntaxContext};
 
 use crate::{CfgAtom, CfgExpr, CfgOptions, DnfExpr};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 struct DummyFile;
-impl Span for DummyFile {
+impl SpanAnchor for DummyFile {
     const DUMMY: Self = DummyFile;
 }
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+struct DummyCtx;
+impl SyntaxContext for DummyCtx {
+    const DUMMY: Self = DummyCtx;
+}
 
 fn assert_parse_result(input: &str, expected: CfgExpr) {
     let source_file = ast::SourceFile::parse(input).ok().unwrap();
     let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-    let tt = syntax_node_to_token_tree(tt.syntax(), DummyFile, 0.into(), &Default::default());
+    let tt = syntax_node_to_token_tree::<_, DummyCtx>(
+        tt.syntax(),
+        DummyFile,
+        0.into(),
+        &Default::default(),
+    );
     let cfg = CfgExpr::parse(&tt);
     assert_eq!(cfg, expected);
 }
@@ -23,7 +33,12 @@ fn assert_parse_result(input: &str, expected: CfgExpr) {
 fn check_dnf(input: &str, expect: Expect) {
     let source_file = ast::SourceFile::parse(input).ok().unwrap();
     let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-    let tt = syntax_node_to_token_tree(tt.syntax(), DummyFile, 0.into(), &Default::default());
+    let tt = syntax_node_to_token_tree::<_, DummyCtx>(
+        tt.syntax(),
+        DummyFile,
+        0.into(),
+        &Default::default(),
+    );
     let cfg = CfgExpr::parse(&tt);
     let actual = format!("#![cfg({})]", DnfExpr::new(cfg));
     expect.assert_eq(&actual);
@@ -32,7 +47,12 @@ fn check_dnf(input: &str, expect: Expect) {
 fn check_why_inactive(input: &str, opts: &CfgOptions, expect: Expect) {
     let source_file = ast::SourceFile::parse(input).ok().unwrap();
     let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-    let tt = syntax_node_to_token_tree(tt.syntax(), DummyFile, 0.into(), &Default::default());
+    let tt = syntax_node_to_token_tree::<_, DummyCtx>(
+        tt.syntax(),
+        DummyFile,
+        0.into(),
+        &Default::default(),
+    );
     let cfg = CfgExpr::parse(&tt);
     let dnf = DnfExpr::new(cfg);
     let why_inactive = dnf.why_inactive(opts).unwrap().to_string();
@@ -43,7 +63,12 @@ fn check_why_inactive(input: &str, opts: &CfgOptions, expect: Expect) {
 fn check_enable_hints(input: &str, opts: &CfgOptions, expected_hints: &[&str]) {
     let source_file = ast::SourceFile::parse(input).ok().unwrap();
     let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-    let tt = syntax_node_to_token_tree(tt.syntax(), DummyFile, 0.into(), &Default::default());
+    let tt = syntax_node_to_token_tree::<_, DummyCtx>(
+        tt.syntax(),
+        DummyFile,
+        0.into(),
+        &Default::default(),
+    );
     let cfg = CfgExpr::parse(&tt);
     let dnf = DnfExpr::new(cfg);
     let hints = dnf.compute_enable_hints(opts).map(|diff| diff.to_string()).collect::<Vec<_>>();
diff --git a/crates/hir-def/src/attr/tests.rs b/crates/hir-def/src/attr/tests.rs
index ad101e9bdf7..60e5cebd3cb 100644
--- a/crates/hir-def/src/attr/tests.rs
+++ b/crates/hir-def/src/attr/tests.rs
@@ -4,15 +4,25 @@
 use base_db::span::SpanAnchor;
 use mbe::syntax_node_to_token_tree;
 use syntax::{ast, AstNode};
-use tt::Span;
+use tt::{SpanAnchor as _, SyntaxContext};
 
 use crate::attr::{DocAtom, DocExpr};
 
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+struct DummyCtx;
+impl SyntaxContext for DummyCtx {
+    const DUMMY: Self = DummyCtx;
+}
+
 fn assert_parse_result(input: &str, expected: DocExpr) {
     let source_file = ast::SourceFile::parse(input).ok().unwrap();
     let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-    let tt =
-        syntax_node_to_token_tree(tt.syntax(), SpanAnchor::DUMMY, 0.into(), &Default::default());
+    let tt = syntax_node_to_token_tree::<_, DummyCtx>(
+        tt.syntax(),
+        SpanAnchor::DUMMY,
+        0.into(),
+        &Default::default(),
+    );
     let cfg = DocExpr::parse(&tt);
     assert_eq!(cfg, expected);
 }
diff --git a/crates/hir-expand/src/attrs.rs b/crates/hir-expand/src/attrs.rs
index 9652dd345a8..01a66cd03ab 100644
--- a/crates/hir-expand/src/attrs.rs
+++ b/crates/hir-expand/src/attrs.rs
@@ -1,7 +1,7 @@
 //! A higher level attributes based on TokenTree, with also some shortcuts.
 use std::{fmt, ops};
 
-use ::tt::Span;
+use ::tt::SpanAnchor as _;
 use base_db::{span::SpanAnchor, CrateId};
 use cfg::CfgExpr;
 use either::Either;
diff --git a/crates/hir-expand/src/builtin_fn_macro.rs b/crates/hir-expand/src/builtin_fn_macro.rs
index adbe49473ac..2a541a36735 100644
--- a/crates/hir-expand/src/builtin_fn_macro.rs
+++ b/crates/hir-expand/src/builtin_fn_macro.rs
@@ -1,5 +1,6 @@
 //! Builtin macro
 
+use ::tt::Span;
 use base_db::{
     span::{SpanAnchor, ROOT_ERASED_FILE_AST_ID},
     AnchoredPath, Edition, FileId,
@@ -15,7 +16,7 @@ use syntax::{
 use crate::{
     db::ExpandDatabase,
     name, quote,
-    tt::{self, Span},
+    tt::{self},
     EagerCallInfo, ExpandError, ExpandResult, HirFileIdExt, MacroCallId, MacroCallLoc,
 };
 
diff --git a/crates/hir-expand/src/db.rs b/crates/hir-expand/src/db.rs
index 32ba7b2f911..1a68653a6fc 100644
--- a/crates/hir-expand/src/db.rs
+++ b/crates/hir-expand/src/db.rs
@@ -1,8 +1,9 @@
 //! Defines database & queries for macro expansion.
 
+use ::tt::SyntaxContext;
 use base_db::{
     salsa,
-    span::{SpanAnchor, ROOT_ERASED_FILE_AST_ID},
+    span::{SpanAnchor, SyntaxContextId, ROOT_ERASED_FILE_AST_ID},
     CrateId, Edition, SourceDatabase,
 };
 use either::Either;
@@ -15,11 +16,13 @@ use syntax::{
 use triomphe::Arc;
 
 use crate::{
-    ast_id_map::AstIdMap, builtin_attr_macro::pseudo_derive_attr_expansion,
-    builtin_fn_macro::EagerExpander, hygiene::HygieneFrame, tt, AstId, BuiltinAttrExpander,
-    BuiltinDeriveExpander, BuiltinFnLikeExpander, EagerCallInfo, ExpandError, ExpandResult,
-    ExpandTo, HirFileId, HirFileIdRepr, MacroCallId, MacroCallKind, MacroCallLoc, MacroDefId,
-    MacroDefKind, MacroFile, ProcMacroExpander, SpanMap, SyntaxContext, SyntaxContextId,
+    ast_id_map::AstIdMap,
+    builtin_attr_macro::pseudo_derive_attr_expansion,
+    builtin_fn_macro::EagerExpander,
+    hygiene::{self, HygieneFrame, SyntaxContextData},
+    tt, AstId, BuiltinAttrExpander, BuiltinDeriveExpander, BuiltinFnLikeExpander, EagerCallInfo,
+    ExpandError, ExpandResult, ExpandTo, HirFileId, HirFileIdRepr, MacroCallId, MacroCallKind,
+    MacroCallLoc, MacroDefId, MacroDefKind, MacroFile, ProcMacroExpander, SpanMap,
 };
 
 /// Total limit on the number of tokens produced by any macro invocation.
@@ -89,7 +92,15 @@ pub trait ExpandDatabase: SourceDatabase {
     #[salsa::interned]
     fn intern_macro_call(&self, macro_call: MacroCallLoc) -> MacroCallId;
     #[salsa::interned]
-    fn intern_syntax_context(&self, ctx: SyntaxContext) -> SyntaxContextId;
+    fn intern_syntax_context(&self, ctx: SyntaxContextData) -> SyntaxContextId;
+    #[salsa::transparent]
+    #[salsa::invoke(hygiene::apply_mark)]
+    fn apply_mark(
+        &self,
+        ctxt: SyntaxContextData,
+        file_id: HirFileId,
+        transparency: hygiene::Transparency,
+    ) -> SyntaxContextId;
 
     /// Lowers syntactic macro call to a token tree representation. That's a firewall
     /// query, only typing in the macro call itself changes the returned
@@ -225,6 +236,7 @@ pub fn expand_speculative(
         .ranges_with_span(tt::SpanData {
             range: token_to_map.text_range(),
             anchor: SpanAnchor { file_id, ast_id: ROOT_ERASED_FILE_AST_ID },
+            ctx: SyntaxContextId::DUMMY,
         })
         .filter_map(|range| syntax_node.covering_element(range).into_token())
         .min_by_key(|t| {
diff --git a/crates/hir-expand/src/hygiene.rs b/crates/hir-expand/src/hygiene.rs
index ce421d3dcd8..e0688178ffb 100644
--- a/crates/hir-expand/src/hygiene.rs
+++ b/crates/hir-expand/src/hygiene.rs
@@ -2,71 +2,92 @@
 //!
 //! Specifically, `ast` + `Hygiene` allows you to create a `Name`. Note that, at
 //! this moment, this is horribly incomplete and handles only `$crate`.
-use base_db::CrateId;
-use db::TokenExpander;
+use base_db::{span::SyntaxContextId, CrateId};
 use either::Either;
 use syntax::{
-    ast::{self, HasDocComments},
-    AstNode, SyntaxNode, TextRange, TextSize,
+    ast::{self},
+    TextRange,
 };
 use triomphe::Arc;
 
 use crate::{
-    db::{self, ExpandDatabase},
+    db::ExpandDatabase,
     name::{AsName, Name},
-    HirFileId, InFile, MacroCallKind, MacroCallLoc, MacroDefKind, MacroFile, SpanMap,
+    HirFileId, InFile,
 };
 
-#[derive(Clone, Debug)]
-pub struct Hygiene {
-    frames: Option<HygieneFrames>,
+#[derive(Debug, Clone, Hash, PartialEq, Eq)]
+pub struct SyntaxContextData {
+    // FIXME: This might only need to be Option<MacroCallId>?
+    outer_expn: HirFileId,
+    outer_transparency: Transparency,
+    parent: SyntaxContextId,
+    /// This context, but with all transparent and semi-transparent expansions filtered away.
+    opaque: SyntaxContextId,
+    /// This context, but with all transparent expansions filtered away.
+    opaque_and_semitransparent: SyntaxContextId,
+    /// Name of the crate to which `$crate` with this context would resolve.
+    dollar_crate_name: Name,
+}
+
+/// A property of a macro expansion that determines how identifiers
+/// produced by that expansion are resolved.
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Hash, Debug)]
+pub enum Transparency {
+    /// Identifier produced by a transparent expansion is always resolved at call-site.
+    /// Call-site spans in procedural macros, hygiene opt-out in `macro` should use this.
+    Transparent,
+    /// Identifier produced by a semi-transparent expansion may be resolved
+    /// either at call-site or at definition-site.
+    /// If it's a local variable, label or `$crate` then it's resolved at def-site.
+    /// Otherwise it's resolved at call-site.
+    /// `macro_rules` macros behave like this, built-in macros currently behave like this too,
+    /// but that's an implementation detail.
+    SemiTransparent,
+    /// Identifier produced by an opaque expansion is always resolved at definition-site.
+    /// Def-site spans in procedural macros, identifiers from `macro` by default use this.
+    Opaque,
+}
+
+pub(super) fn apply_mark(
+    _db: &dyn ExpandDatabase,
+    _ctxt: SyntaxContextData,
+    _file_id: HirFileId,
+    _transparency: Transparency,
+) -> SyntaxContextId {
+    _db.intern_syntax_context(_ctxt)
 }
 
+// pub(super) fn with_ctxt_from_mark(db: &ExpandDatabase, file_id: HirFileId) {
+//     self.with_ctxt_from_mark(expn_id, Transparency::Transparent)
+// }
+// pub(super) fn with_call_site_ctxt(db: &ExpandDatabase, file_id: HirFileId) {
+//     self.with_ctxt_from_mark(expn_id, Transparency::Transparent)
+// }
+
+#[derive(Clone, Debug)]
+pub struct Hygiene {}
+
 impl Hygiene {
-    pub fn new(db: &dyn ExpandDatabase, file_id: HirFileId) -> Hygiene {
-        Hygiene { frames: Some(HygieneFrames::new(db, file_id)) }
+    pub fn new(_: &dyn ExpandDatabase, _: HirFileId) -> Hygiene {
+        Hygiene {}
     }
 
     pub fn new_unhygienic() -> Hygiene {
-        Hygiene { frames: None }
+        Hygiene {}
     }
 
     // FIXME: this should just return name
     pub fn name_ref_to_name(
         &self,
-        db: &dyn ExpandDatabase,
+        _: &dyn ExpandDatabase,
         name_ref: ast::NameRef,
     ) -> Either<Name, CrateId> {
-        if let Some(frames) = &self.frames {
-            if name_ref.text() == "$crate" {
-                if let Some(krate) = frames.root_crate(db, name_ref.syntax()) {
-                    return Either::Right(krate);
-                }
-            }
-        }
-
         Either::Left(name_ref.as_name())
     }
 
-    pub fn local_inner_macros(&self, _db: &dyn ExpandDatabase, path: ast::Path) -> Option<CrateId> {
-        let mut _token = path.syntax().first_token()?.text_range();
-        let frames = self.frames.as_ref()?;
-        let mut _current = &frames.0;
-
-        // FIXME: Hygiene ...
-        return None;
-        // loop {
-        //     let (mapped, origin) = current.expansion.as_ref()?.map_ident_up(db, token)?;
-        //     if origin == Origin::Def {
-        //         return if current.local_inner {
-        //             frames.root_crate(db, path.syntax())
-        //         } else {
-        //             None
-        //         };
-        //     }
-        //     current = current.call_site.as_ref()?;
-        //     token = mapped.value;
-        // }
+    pub fn local_inner_macros(&self, _: &dyn ExpandDatabase, _: ast::Path) -> Option<CrateId> {
+        None
     }
 }
 
@@ -74,150 +95,19 @@ impl Hygiene {
 struct HygieneFrames(Arc<HygieneFrame>);
 
 #[derive(Clone, Debug, Eq, PartialEq)]
-pub struct HygieneFrame {
-    expansion: Option<HygieneInfo>,
-
-    // Indicate this is a local inner macro
-    local_inner: bool,
-    krate: Option<CrateId>,
-
-    call_site: Option<Arc<HygieneFrame>>,
-    def_site: Option<Arc<HygieneFrame>>,
-}
-
-impl HygieneFrames {
-    fn new(db: &dyn ExpandDatabase, file_id: HirFileId) -> Self {
-        // Note that this intentionally avoids the `hygiene_frame` query to avoid blowing up memory
-        // usage. The query is only helpful for nested `HygieneFrame`s as it avoids redundant work.
-        HygieneFrames(Arc::new(HygieneFrame::new(db, file_id)))
-    }
-
-    fn root_crate(&self, _db: &dyn ExpandDatabase, node: &SyntaxNode) -> Option<CrateId> {
-        let mut _token = node.first_token()?.text_range();
-        let mut _result = self.0.krate;
-        let mut _current = self.0.clone();
-
-        return None;
-
-        //     while let Some((mapped, origin)) =
-        //         current.expansion.as_ref().and_then(|it| it.map_ident_up(db, token))
-        //     {
-        //         result = current.krate;
-
-        //         let site = match origin {
-        //             Origin::Def => &current.def_site,
-        //             Origin::Call => &current.call_site,
-        //         };
-
-        //         let site = match site {
-        //             None => break,
-        //             Some(it) => it,
-        //         };
-
-        //         current = site.clone();
-        //         token = mapped.value;
-        //     }
-
-        //     result
-    }
-}
+pub struct HygieneFrame {}
 
 #[derive(Debug, Clone, PartialEq, Eq)]
-struct HygieneInfo {
-    file: MacroFile,
-    /// The start offset of the `macro_rules!` arguments or attribute input.
-    attr_input_or_mac_def_start: Option<InFile<TextSize>>,
-
-    macro_def: TokenExpander,
-    macro_arg: Arc<crate::tt::Subtree>,
-    exp_map: Arc<SpanMap>,
-}
+struct HygieneInfo {}
 
 impl HygieneInfo {
-    fn _map_ident_up(
-        &self,
-        _db: &dyn ExpandDatabase,
-        _token: TextRange,
-    ) -> Option<InFile<TextRange>> {
-        // self.exp_map.token_by_range(token).map(|span| InFile::new(span.anchor, span.range))
+    fn _map_ident_up(&self, _: &dyn ExpandDatabase, _: TextRange) -> Option<InFile<TextRange>> {
         None
     }
 }
 
-fn make_hygiene_info(
-    db: &dyn ExpandDatabase,
-    macro_file: MacroFile,
-    loc: &MacroCallLoc,
-) -> HygieneInfo {
-    let def = loc.def.ast_id().left().and_then(|id| {
-        let def_tt = match id.to_node(db) {
-            ast::Macro::MacroRules(mac) => mac.token_tree()?,
-            ast::Macro::MacroDef(mac) => mac.body()?,
-        };
-        Some(InFile::new(id.file_id, def_tt))
-    });
-    let attr_input_or_mac_def = def.or_else(|| match loc.kind {
-        MacroCallKind::Attr { ast_id, invoc_attr_index, .. } => {
-            let tt = ast_id
-                .to_node(db)
-                .doc_comments_and_attrs()
-                .nth(invoc_attr_index.ast_index())
-                .and_then(Either::left)?
-                .token_tree()?;
-            Some(InFile::new(ast_id.file_id, tt))
-        }
-        _ => None,
-    });
-
-    let macro_def = db.macro_expander(loc.def);
-    let (_, exp_map) = db.parse_macro_expansion(macro_file).value;
-    let macro_arg = db.macro_arg(macro_file.macro_call_id).value.unwrap_or_else(|| {
-        Arc::new(tt::Subtree { delimiter: tt::Delimiter::UNSPECIFIED, token_trees: Vec::new() })
-    });
-
-    HygieneInfo {
-        file: macro_file,
-        attr_input_or_mac_def_start: attr_input_or_mac_def
-            .map(|it| it.map(|tt| tt.syntax().text_range().start())),
-        macro_arg,
-        macro_def,
-        exp_map,
-    }
-}
-
 impl HygieneFrame {
-    pub(crate) fn new(db: &dyn ExpandDatabase, file_id: HirFileId) -> HygieneFrame {
-        let (info, krate, local_inner) = match file_id.macro_file() {
-            None => (None, None, false),
-            Some(macro_file) => {
-                let loc = db.lookup_intern_macro_call(macro_file.macro_call_id);
-                let info = Some((make_hygiene_info(db, macro_file, &loc), loc.kind.file_id()));
-                match loc.def.kind {
-                    MacroDefKind::Declarative(_) => {
-                        (info, Some(loc.def.krate), loc.def.local_inner)
-                    }
-                    MacroDefKind::BuiltIn(..) => (info, Some(loc.def.krate), false),
-                    MacroDefKind::BuiltInAttr(..) => (info, None, false),
-                    MacroDefKind::BuiltInDerive(..) => (info, None, false),
-                    MacroDefKind::BuiltInEager(..) => (info, None, false),
-                    MacroDefKind::ProcMacro(..) => (info, None, false),
-                }
-            }
-        };
-
-        let Some((info, calling_file)) = info else {
-            return HygieneFrame {
-                expansion: None,
-                local_inner,
-                krate,
-                call_site: None,
-                def_site: None,
-            };
-        };
-
-        let def_site = info.attr_input_or_mac_def_start.map(|it| db.hygiene_frame(it.file_id));
-        let call_site = Some(db.hygiene_frame(calling_file));
-
-        HygieneFrame { expansion: Some(info), local_inner, krate, call_site, def_site }
+    pub(crate) fn new(_: &dyn ExpandDatabase, _: HirFileId) -> HygieneFrame {
+        HygieneFrame {}
     }
 }
diff --git a/crates/hir-expand/src/lib.rs b/crates/hir-expand/src/lib.rs
index bd5796e000a..ae07cf4b151 100644
--- a/crates/hir-expand/src/lib.rs
+++ b/crates/hir-expand/src/lib.rs
@@ -51,7 +51,7 @@ pub type DeclarativeMacro = ::mbe::DeclarativeMacro<tt::SpanData>;
 
 pub mod tt {
     pub use base_db::span::SpanData;
-    pub use tt::{DelimiterKind, Spacing, Span};
+    pub use tt::{DelimiterKind, Spacing, Span, SpanAnchor};
 
     pub type Delimiter = ::tt::Delimiter<SpanData>;
     pub type Subtree = ::tt::Subtree<SpanData>;
@@ -97,44 +97,6 @@ impl fmt::Display for ExpandError {
     }
 }
 
-/// `MacroCallId` identifies a particular macro invocation, like
-/// `println!("Hello, {}", world)`.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct SyntaxContextId(base_db::salsa::InternId);
-base_db::impl_intern_key!(SyntaxContextId);
-
-#[derive(Debug, Clone, Hash, PartialEq, Eq)]
-pub struct SyntaxContext {
-    outer_expn: HirFileId,
-    outer_transparency: Transparency,
-    parent: SyntaxContextId,
-    /// This context, but with all transparent and semi-transparent expansions filtered away.
-    opaque: SyntaxContextId,
-    /// This context, but with all transparent expansions filtered away.
-    opaque_and_semitransparent: SyntaxContextId,
-    /// Name of the crate to which `$crate` with this context would resolve.
-    dollar_crate_name: name::Name,
-}
-
-/// A property of a macro expansion that determines how identifiers
-/// produced by that expansion are resolved.
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Hash, Debug)]
-pub enum Transparency {
-    /// Identifier produced by a transparent expansion is always resolved at call-site.
-    /// Call-site spans in procedural macros, hygiene opt-out in `macro` should use this.
-    Transparent,
-    /// Identifier produced by a semi-transparent expansion may be resolved
-    /// either at call-site or at definition-site.
-    /// If it's a local variable, label or `$crate` then it's resolved at def-site.
-    /// Otherwise it's resolved at call-site.
-    /// `macro_rules` macros behave like this, built-in macros currently behave like this too,
-    /// but that's an implementation detail.
-    SemiTransparent,
-    /// Identifier produced by an opaque expansion is always resolved at definition-site.
-    /// Def-site spans in procedural macros, identifiers from `macro` by default use this.
-    Opaque,
-}
-
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct MacroCallLoc {
     pub def: MacroDefId,
diff --git a/crates/hir-expand/src/quote.rs b/crates/hir-expand/src/quote.rs
index 9dd4965c150..44f20cbd92d 100644
--- a/crates/hir-expand/src/quote.rs
+++ b/crates/hir-expand/src/quote.rs
@@ -247,8 +247,8 @@ mod tests {
         assert_eq!(quoted.to_string(), "hello");
         let t = format!("{quoted:?}");
         expect![[r#"
-            SUBTREE $$ SpanData { range: 0..0, anchor: SpanAnchor { file_id: FileId(0), ast_id: Idx::<RustLanguage>>(0) } } SpanData { range: 0..0, anchor: SpanAnchor { file_id: FileId(0), ast_id: Idx::<RustLanguage>>(0) } }
-              IDENT   hello SpanData { range: 0..0, anchor: SpanAnchor { file_id: FileId(0), ast_id: Idx::<RustLanguage>>(0) } }"#]].assert_eq(&t);
+            SUBTREE $$ SpanData { range: 0..0, anchor: SpanAnchor(FileId(0), 0), ctx: SyntaxContextId(0) } SpanData { range: 0..0, anchor: SpanAnchor(FileId(0), 0), ctx: SyntaxContextId(0) }
+              IDENT   hello SpanData { range: 0..0, anchor: SpanAnchor(FileId(0), 0), ctx: SyntaxContextId(0) }"#]].assert_eq(&t);
     }
 
     #[test]
diff --git a/crates/mbe/src/benchmark.rs b/crates/mbe/src/benchmark.rs
index 4f60e90773e..2ead7164563 100644
--- a/crates/mbe/src/benchmark.rs
+++ b/crates/mbe/src/benchmark.rs
@@ -6,19 +6,27 @@ use syntax::{
     AstNode, SmolStr,
 };
 use test_utils::{bench, bench_fixture, skip_slow_tests};
-use tt::{Span, SpanData};
+use tt::{Span, SpanAnchor, SyntaxContext};
 
 use crate::{
     parser::{MetaVarKind, Op, RepeatKind, Separator},
     syntax_node_to_token_tree, DeclarativeMacro,
 };
 
+type SpanData = tt::SpanData<DummyFile, DummyCtx>;
+
 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
 struct DummyFile;
-impl Span for DummyFile {
+impl SpanAnchor for DummyFile {
     const DUMMY: Self = DummyFile;
 }
 
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+struct DummyCtx;
+impl SyntaxContext for DummyCtx {
+    const DUMMY: Self = DummyCtx;
+}
+
 #[test]
 fn benchmark_parse_macro_rules() {
     if skip_slow_tests() {
@@ -54,14 +62,14 @@ fn benchmark_expand_macro_rules() {
     assert_eq!(hash, 69413);
 }
 
-fn macro_rules_fixtures() -> FxHashMap<String, DeclarativeMacro<SpanData<DummyFile>>> {
+fn macro_rules_fixtures() -> FxHashMap<String, DeclarativeMacro<SpanData>> {
     macro_rules_fixtures_tt()
         .into_iter()
         .map(|(id, tt)| (id, DeclarativeMacro::parse_macro_rules(&tt, true)))
         .collect()
 }
 
-fn macro_rules_fixtures_tt() -> FxHashMap<String, tt::Subtree<SpanData<DummyFile>>> {
+fn macro_rules_fixtures_tt() -> FxHashMap<String, tt::Subtree<SpanData>> {
     let fixture = bench_fixture::numerous_macro_rules();
     let source_file = ast::SourceFile::parse(&fixture).ok().unwrap();
 
@@ -84,8 +92,8 @@ fn macro_rules_fixtures_tt() -> FxHashMap<String, tt::Subtree<SpanData<DummyFile
 
 /// Generate random invocation fixtures from rules
 fn invocation_fixtures(
-    rules: &FxHashMap<String, DeclarativeMacro<SpanData<DummyFile>>>,
-) -> Vec<(String, tt::Subtree<SpanData<DummyFile>>)> {
+    rules: &FxHashMap<String, DeclarativeMacro<SpanData>>,
+) -> Vec<(String, tt::Subtree<SpanData>)> {
     let mut seed = 123456789;
     let mut res = Vec::new();
 
@@ -130,11 +138,7 @@ fn invocation_fixtures(
     }
     return res;
 
-    fn collect_from_op(
-        op: &Op<SpanData<DummyFile>>,
-        parent: &mut tt::Subtree<SpanData<DummyFile>>,
-        seed: &mut usize,
-    ) {
+    fn collect_from_op(op: &Op<SpanData>, parent: &mut tt::Subtree<SpanData>, seed: &mut usize) {
         return match op {
             Op::Var { kind, .. } => match kind.as_ref() {
                 Some(MetaVarKind::Ident) => parent.token_trees.push(make_ident("foo")),
@@ -220,20 +224,20 @@ fn invocation_fixtures(
             *seed = usize::wrapping_add(usize::wrapping_mul(*seed, a), c);
             *seed
         }
-        fn make_ident(ident: &str) -> tt::TokenTree<SpanData<DummyFile>> {
+        fn make_ident(ident: &str) -> tt::TokenTree<SpanData> {
             tt::Leaf::Ident(tt::Ident { span: SpanData::DUMMY, text: SmolStr::new(ident) }).into()
         }
-        fn make_punct(char: char) -> tt::TokenTree<SpanData<DummyFile>> {
+        fn make_punct(char: char) -> tt::TokenTree<SpanData> {
             tt::Leaf::Punct(tt::Punct { span: SpanData::DUMMY, char, spacing: tt::Spacing::Alone })
                 .into()
         }
-        fn make_literal(lit: &str) -> tt::TokenTree<SpanData<DummyFile>> {
+        fn make_literal(lit: &str) -> tt::TokenTree<SpanData> {
             tt::Leaf::Literal(tt::Literal { span: SpanData::DUMMY, text: SmolStr::new(lit) }).into()
         }
         fn make_subtree(
             kind: tt::DelimiterKind,
-            token_trees: Option<Vec<tt::TokenTree<SpanData<DummyFile>>>>,
-        ) -> tt::TokenTree<SpanData<DummyFile>> {
+            token_trees: Option<Vec<tt::TokenTree<SpanData>>>,
+        ) -> tt::TokenTree<SpanData> {
             tt::Subtree {
                 delimiter: tt::Delimiter { open: SpanData::DUMMY, close: SpanData::DUMMY, kind },
                 token_trees: token_trees.unwrap_or_default(),
diff --git a/crates/mbe/src/syntax_bridge.rs b/crates/mbe/src/syntax_bridge.rs
index c8c2e5dcd55..ab272862cdb 100644
--- a/crates/mbe/src/syntax_bridge.rs
+++ b/crates/mbe/src/syntax_bridge.rs
@@ -9,7 +9,7 @@ use syntax::{
 };
 use tt::{
     buffer::{Cursor, TokenBuffer},
-    Span, SpanData,
+    Span, SpanData, SyntaxContext,
 };
 
 use crate::{to_parser_input::to_parser_input, tt_iter::TtIter, TokenMap};
@@ -23,33 +23,37 @@ mod tests;
 /// to relative spans, relative to the passed anchor.
 /// `map` is used to resolve the converted spans accordingly.
 /// TODO: Flesh out the doc comment more thoroughly
-pub fn syntax_node_to_token_tree<SpanAnchor: Copy>(
+pub fn syntax_node_to_token_tree<Anchor, Ctx>(
     node: &SyntaxNode,
-    anchor: SpanAnchor,
+    anchor: Anchor,
     anchor_offset: TextSize,
-    map: &TokenMap<SpanData<SpanAnchor>>,
-) -> tt::Subtree<SpanData<SpanAnchor>>
+    map: &TokenMap<SpanData<Anchor, Ctx>>,
+) -> tt::Subtree<SpanData<Anchor, Ctx>>
 where
-    SpanData<SpanAnchor>: Span,
+    SpanData<Anchor, Ctx>: Span,
+    Anchor: Copy,
+    Ctx: SyntaxContext,
 {
     assert!(anchor_offset <= node.text_range().start());
-    let mut c = Converter::new(node, anchor_offset, anchor, vec![], map);
-    convert_tokens(&mut c)
+    let mut c = Converter::new(node, anchor_offset, vec![], map);
+    convert_tokens(&mut c, anchor)
 }
 
-pub fn syntax_node_to_token_tree_censored<SpanAnchor: Copy>(
+pub fn syntax_node_to_token_tree_censored<Anchor, Ctx>(
     node: &SyntaxNode,
-    anchor: SpanAnchor,
+    anchor: Anchor,
     anchor_offset: TextSize,
-    map: &TokenMap<SpanData<SpanAnchor>>,
+    map: &TokenMap<SpanData<Anchor, Ctx>>,
     censored: Vec<SyntaxNode>,
-) -> tt::Subtree<SpanData<SpanAnchor>>
+) -> tt::Subtree<SpanData<Anchor, Ctx>>
 where
-    SpanData<SpanAnchor>: Span,
+    SpanData<Anchor, Ctx>: Span,
+    Anchor: Copy,
+    Ctx: SyntaxContext,
 {
     assert!(anchor_offset <= node.text_range().start());
-    let mut c = Converter::new(node, anchor_offset, anchor, censored, map);
-    convert_tokens(&mut c)
+    let mut c = Converter::new(node, anchor_offset, censored, map);
+    convert_tokens(&mut c, anchor)
 }
 
 // The following items are what `rustc` macro can be parsed into :
@@ -64,12 +68,14 @@ where
 // * AssocItems(SmallVec<[ast::AssocItem; 1]>)
 // * ForeignItems(SmallVec<[ast::ForeignItem; 1]>
 
-pub fn token_tree_to_syntax_node<SpanAnchor: Copy>(
-    tt: &tt::Subtree<SpanData<SpanAnchor>>,
+pub fn token_tree_to_syntax_node<Anchor, Ctx>(
+    tt: &tt::Subtree<SpanData<Anchor, Ctx>>,
     entry_point: parser::TopEntryPoint,
-) -> (Parse<SyntaxNode>, TokenMap<SpanData<SpanAnchor>>)
+) -> (Parse<SyntaxNode>, TokenMap<SpanData<Anchor, Ctx>>)
 where
-    SpanData<SpanAnchor>: Span,
+    SpanData<Anchor, Ctx>: Span,
+    Anchor: Copy,
+    Ctx: SyntaxContext,
 {
     let buffer = match tt {
         tt::Subtree {
@@ -97,36 +103,42 @@ where
     tree_sink.finish()
 }
 
-pub fn map_from_syntax_node<SpanAnchor>(
+pub fn map_from_syntax_node<Anchor, Ctx>(
     node: &SyntaxNode,
-    anchor: SpanAnchor,
+    anchor: Anchor,
     anchor_offset: TextSize,
-) -> TokenMap<SpanData<SpanAnchor>>
+) -> TokenMap<SpanData<Anchor, Ctx>>
 where
-    SpanAnchor: Copy,
-    SpanData<SpanAnchor>: Span,
+    Anchor: Copy,
+    SpanData<Anchor, Ctx>: Span,
+    Ctx: SyntaxContext,
 {
     let mut map = TokenMap::default();
     node.descendants_with_tokens().filter_map(NodeOrToken::into_token).for_each(|t| {
-        map.insert(t.text_range(), SpanData { range: t.text_range() - anchor_offset, anchor });
+        map.insert(
+            t.text_range(),
+            SpanData { range: t.text_range() - anchor_offset, anchor, ctx: Ctx::DUMMY },
+        );
     });
     map
 }
 
 /// Convert a string to a `TokenTree`
-pub fn parse_to_token_tree<SpanAnchor: Copy>(
+pub fn parse_to_token_tree<Anchor, Ctx>(
     text: &str,
-    file_id: SpanAnchor,
-) -> Option<tt::Subtree<SpanData<SpanAnchor>>>
+    anchor: Anchor,
+) -> Option<tt::Subtree<SpanData<Anchor, Ctx>>>
 where
-    SpanData<SpanAnchor>: Span,
+    SpanData<Anchor, Ctx>: Span,
+    Anchor: Copy,
+    Ctx: SyntaxContext,
 {
     let lexed = parser::LexedStr::new(text);
     if lexed.errors().next().is_some() {
         return None;
     }
-    let mut conv = RawConverter { lexed, pos: 0, _offset: TextSize::default(), file_id };
-    Some(convert_tokens(&mut conv))
+    let mut conv = RawConverter { lexed, pos: 0, _offset: TextSize::default() };
+    Some(convert_tokens(&mut conv, anchor))
 }
 
 /// Split token tree with separate expr: $($e:expr)SEP*
@@ -166,134 +178,141 @@ pub fn parse_exprs_with_sep<S: Span>(tt: &tt::Subtree<S>, sep: char) -> Vec<tt::
     res
 }
 
-fn convert_tokens<SpanAnchor, C: TokenConverter<SpanAnchor>>(
+fn convert_tokens<Anchor, Ctx, C>(
     conv: &mut C,
-) -> tt::Subtree<SpanData<SpanAnchor>>
+    anchor: Anchor,
+) -> tt::Subtree<SpanData<Anchor, Ctx>>
 where
-    SpanData<SpanAnchor>: Span,
-    SpanAnchor: Copy,
+    C: TokenConverter<Anchor, Ctx>,
+    Ctx: SyntaxContext,
+    SpanData<Anchor, Ctx>: Span,
+    Anchor: Copy,
 {
-    let entry = tt::Subtree { delimiter: tt::Delimiter::unspecified(), token_trees: vec![] };
+    let entry = tt::Subtree { delimiter: tt::Delimiter::UNSPECIFIED, token_trees: vec![] };
     let mut stack = NonEmptyVec::new(entry);
-    let anchor = conv.anchor();
 
-    loop {
-        let subtree = stack.last_mut();
-        let result = &mut subtree.token_trees;
-        let Some((token, rel_range, abs_range)) = conv.bump() else { break };
+    while let Some((token, rel_range, abs_range)) = conv.bump() {
+        let tt::Subtree { delimiter, token_trees: result } = stack.last_mut();
+        let mk_dummy_span = || SpanData { range: rel_range, anchor, ctx: Ctx::DUMMY };
 
         let kind = token.kind(conv);
-        if kind == COMMENT {
-            if let Some(tokens) = conv.convert_doc_comment(
-                &token,
-                conv.span_for(abs_range).unwrap_or(SpanData { range: rel_range, anchor }),
-            ) {
-                result.extend(tokens);
+
+        let tt = match kind {
+            // Desugar doc comments into doc attributes
+            COMMENT => {
+                let span = conv.span_for(abs_range).unwrap_or_else(mk_dummy_span);
+                if let Some(tokens) = conv.convert_doc_comment(&token, span) {
+                    result.extend(tokens);
+                }
+                continue;
             }
-            continue;
-        }
-        let tt = if kind.is_punct() && kind != UNDERSCORE {
-            let expected = match subtree.delimiter.kind {
-                tt::DelimiterKind::Parenthesis => Some(T![')']),
-                tt::DelimiterKind::Brace => Some(T!['}']),
-                tt::DelimiterKind::Bracket => Some(T![']']),
-                tt::DelimiterKind::Invisible => None,
-            };
+            _ if kind.is_punct() && kind != UNDERSCORE => {
+                let expected = match delimiter.kind {
+                    tt::DelimiterKind::Parenthesis => Some(T![')']),
+                    tt::DelimiterKind::Brace => Some(T!['}']),
+                    tt::DelimiterKind::Bracket => Some(T![']']),
+                    tt::DelimiterKind::Invisible => None,
+                };
 
-            if let Some(expected) = expected {
-                if kind == expected {
+                // Current token is a closing delimiter that we expect, fix up the closing span
+                // and end the subtree here
+                if matches!(expected, Some(expected) if expected == kind) {
                     if let Some(mut subtree) = stack.pop() {
-                        subtree.delimiter.close = conv
-                            .span_for(abs_range)
-                            .unwrap_or(SpanData { range: rel_range, anchor });
+                        subtree.delimiter.close =
+                            conv.span_for(abs_range).unwrap_or_else(mk_dummy_span);
                         stack.last_mut().token_trees.push(subtree.into());
                     }
                     continue;
                 }
-            }
-
-            let delim = match kind {
-                T!['('] => Some(tt::DelimiterKind::Parenthesis),
-                T!['{'] => Some(tt::DelimiterKind::Brace),
-                T!['['] => Some(tt::DelimiterKind::Bracket),
-                _ => None,
-            };
 
-            if let Some(kind) = delim {
-                let subtree = tt::Subtree {
-                    delimiter: tt::Delimiter {
-                        // FIXME: Open and close spans
-                        open: conv
-                            .span_for(abs_range)
-                            .unwrap_or(SpanData { range: rel_range, anchor }),
-                        close: Span::DUMMY,
-                        kind,
-                    },
-                    token_trees: vec![],
+                let delim = match kind {
+                    T!['('] => Some(tt::DelimiterKind::Parenthesis),
+                    T!['{'] => Some(tt::DelimiterKind::Brace),
+                    T!['['] => Some(tt::DelimiterKind::Bracket),
+                    _ => None,
                 };
-                stack.push(subtree);
-                continue;
-            }
 
-            let spacing = match conv.peek().map(|next| next.kind(conv)) {
-                Some(kind) if is_single_token_op(kind) => tt::Spacing::Joint,
-                _ => tt::Spacing::Alone,
-            };
-            let char = match token.to_char(conv) {
-                Some(c) => c,
-                None => {
-                    panic!("Token from lexer must be single char: token = {token:#?}");
+                // Start a new subtree
+                if let Some(kind) = delim {
+                    stack.push(tt::Subtree {
+                        delimiter: tt::Delimiter {
+                            open: conv.span_for(abs_range).unwrap_or_else(mk_dummy_span),
+                            // will be overwritten on subtree close above
+                            close: mk_dummy_span(),
+                            kind,
+                        },
+                        token_trees: vec![],
+                    });
+                    continue;
                 }
-            };
-            tt::Leaf::from(tt::Punct {
-                char,
-                spacing,
-                span: conv.span_for(abs_range).unwrap_or(SpanData { range: rel_range, anchor }),
-            })
-            .into()
-        } else {
-            macro_rules! make_leaf {
-                ($i:ident) => {
-                    tt::$i {
-                        span: conv
-                            .span_for(abs_range)
-                            .unwrap_or(SpanData { range: rel_range, anchor }),
-                        text: token.to_text(conv),
-                    }
-                    .into()
+
+                let spacing = match conv.peek().map(|next| next.kind(conv)) {
+                    Some(kind) if is_single_token_op(kind) => tt::Spacing::Joint,
+                    _ => tt::Spacing::Alone,
                 };
+                let Some(char) = token.to_char(conv) else {
+                    panic!("Token from lexer must be single char: token = {token:#?}")
+                };
+                tt::Leaf::from(tt::Punct {
+                    char,
+                    spacing,
+                    span: conv.span_for(abs_range).unwrap_or_else(mk_dummy_span),
+                })
+                .into()
             }
-            let leaf: tt::Leaf<_> = match kind {
-                T![true] | T![false] => make_leaf!(Ident),
-                IDENT => make_leaf!(Ident),
-                UNDERSCORE => make_leaf!(Ident),
-                k if k.is_keyword() => make_leaf!(Ident),
-                k if k.is_literal() => make_leaf!(Literal),
-                // FIXME: Check whether span splitting works as intended
-                LIFETIME_IDENT => {
-                    let char_unit = TextSize::of('\'');
-                    let r = TextRange::at(rel_range.start(), char_unit);
-                    let apostrophe = tt::Leaf::from(tt::Punct {
-                        char: '\'',
-                        spacing: tt::Spacing::Joint,
-                        span: conv.span_for(abs_range).unwrap_or(SpanData { range: r, anchor }),
-                    });
-                    result.push(apostrophe.into());
-
-                    let r =
-                        TextRange::at(rel_range.start() + char_unit, rel_range.len() - char_unit);
-                    let ident = tt::Leaf::from(tt::Ident {
-                        text: SmolStr::new(&token.to_text(conv)[1..]),
-                        span: conv.span_for(abs_range).unwrap_or(SpanData { range: r, anchor }),
-                    });
-                    result.push(ident.into());
-                    continue;
+            _ => {
+                macro_rules! make_leaf {
+                    ($i:ident) => {
+                        tt::$i {
+                            span: conv.span_for(abs_range).unwrap_or_else(mk_dummy_span),
+                            text: token.to_text(conv),
+                        }
+                        .into()
+                    };
                 }
-                _ => continue,
-            };
+                let leaf: tt::Leaf<_> = match kind {
+                    T![true] | T![false] => make_leaf!(Ident),
+                    IDENT => make_leaf!(Ident),
+                    UNDERSCORE => make_leaf!(Ident),
+                    k if k.is_keyword() => make_leaf!(Ident),
+                    k if k.is_literal() => make_leaf!(Literal),
+                    // FIXME: Check whether span splitting works as intended
+                    LIFETIME_IDENT => {
+                        let char_unit = TextSize::of('\'');
+                        let r = TextRange::at(rel_range.start(), char_unit);
+                        let apostrophe = tt::Leaf::from(tt::Punct {
+                            char: '\'',
+                            spacing: tt::Spacing::Joint,
+                            span: conv.span_for(abs_range).unwrap_or(SpanData {
+                                range: r,
+                                anchor,
+                                ctx: Ctx::DUMMY,
+                            }),
+                        });
+                        result.push(apostrophe.into());
+
+                        let r = TextRange::at(
+                            rel_range.start() + char_unit,
+                            rel_range.len() - char_unit,
+                        );
+                        let ident = tt::Leaf::from(tt::Ident {
+                            text: SmolStr::new(&token.to_text(conv)[1..]),
+                            span: conv.span_for(abs_range).unwrap_or(SpanData {
+                                range: r,
+                                anchor,
+                                ctx: Ctx::DUMMY,
+                            }),
+                        });
+                        result.push(ident.into());
+                        continue;
+                    }
+                    _ => continue,
+                };
 
-            leaf.into()
+                leaf.into()
+            }
         };
+
         result.push(tt);
     }
 
@@ -417,11 +436,10 @@ fn convert_doc_comment<S: Copy>(
 }
 
 /// A raw token (straight from lexer) converter
-struct RawConverter<'a, SpanAnchor> {
+struct RawConverter<'a> {
     lexed: parser::LexedStr<'a>,
     pos: usize,
     _offset: TextSize,
-    file_id: SpanAnchor,
 }
 
 trait SrcToken<Ctx>: std::fmt::Debug {
@@ -432,48 +450,47 @@ trait SrcToken<Ctx>: std::fmt::Debug {
     fn to_text(&self, ctx: &Ctx) -> SmolStr;
 }
 
-trait TokenConverter<SpanAnchor>: Sized {
+trait TokenConverter<Anchor, Ctx>: Sized {
     type Token: SrcToken<Self>;
 
     fn convert_doc_comment(
         &self,
         token: &Self::Token,
-        span: SpanData<SpanAnchor>,
-    ) -> Option<Vec<tt::TokenTree<SpanData<SpanAnchor>>>>;
+        span: SpanData<Anchor, Ctx>,
+    ) -> Option<Vec<tt::TokenTree<SpanData<Anchor, Ctx>>>>;
 
     fn bump(&mut self) -> Option<(Self::Token, TextRange, TextRange)>;
 
     fn peek(&self) -> Option<Self::Token>;
 
-    fn anchor(&self) -> SpanAnchor;
-    fn span_for(&self, range: TextRange) -> Option<SpanData<SpanAnchor>>;
+    fn span_for(&self, range: TextRange) -> Option<SpanData<Anchor, Ctx>>;
 }
 
-impl<SpanAnchor> SrcToken<RawConverter<'_, SpanAnchor>> for usize {
-    fn kind(&self, ctx: &RawConverter<'_, SpanAnchor>) -> SyntaxKind {
+impl SrcToken<RawConverter<'_>> for usize {
+    fn kind(&self, ctx: &RawConverter<'_>) -> SyntaxKind {
         ctx.lexed.kind(*self)
     }
 
-    fn to_char(&self, ctx: &RawConverter<'_, SpanAnchor>) -> Option<char> {
+    fn to_char(&self, ctx: &RawConverter<'_>) -> Option<char> {
         ctx.lexed.text(*self).chars().next()
     }
 
-    fn to_text(&self, ctx: &RawConverter<'_, SpanAnchor>) -> SmolStr {
+    fn to_text(&self, ctx: &RawConverter<'_>) -> SmolStr {
         ctx.lexed.text(*self).into()
     }
 }
 
-impl<SpanAnchor: Copy> TokenConverter<SpanAnchor> for RawConverter<'_, SpanAnchor>
+impl<Anchor: Copy, Ctx> TokenConverter<Anchor, Ctx> for RawConverter<'_>
 where
-    SpanData<SpanAnchor>: Span,
+    SpanData<Anchor, Ctx>: Span,
 {
     type Token = usize;
 
     fn convert_doc_comment(
         &self,
         &token: &usize,
-        span: SpanData<SpanAnchor>,
-    ) -> Option<Vec<tt::TokenTree<SpanData<SpanAnchor>>>> {
+        span: SpanData<Anchor, Ctx>,
+    ) -> Option<Vec<tt::TokenTree<SpanData<Anchor, Ctx>>>> {
         let text = self.lexed.text(token);
         convert_doc_comment(&doc_comment(text), span)
     }
@@ -497,34 +514,29 @@ where
         Some(self.pos)
     }
 
-    fn anchor(&self) -> SpanAnchor {
-        self.file_id
-    }
-    fn span_for(&self, _: TextRange) -> Option<SpanData<SpanAnchor>> {
+    fn span_for(&self, _: TextRange) -> Option<SpanData<Anchor, Ctx>> {
         None
     }
 }
 
-struct Converter<'a, SpanAnchor> {
+struct Converter<'a, Anchor, Ctx> {
     current: Option<SyntaxToken>,
     preorder: PreorderWithTokens,
     range: TextRange,
     punct_offset: Option<(SyntaxToken, TextSize)>,
     /// Used to make the emitted text ranges in the spans relative to the span anchor.
     offset: TextSize,
-    file_id: SpanAnchor,
-    map: &'a TokenMap<SpanData<SpanAnchor>>,
+    map: &'a TokenMap<SpanData<Anchor, Ctx>>,
     censored: Vec<SyntaxNode>,
 }
 
-impl<'a, SpanAnchor> Converter<'a, SpanAnchor> {
+impl<'a, Anchor, Ctx> Converter<'a, Anchor, Ctx> {
     fn new(
         node: &SyntaxNode,
         anchor_offset: TextSize,
-        file_id: SpanAnchor,
         censored: Vec<SyntaxNode>,
-        map: &'a TokenMap<SpanData<SpanAnchor>>,
-    ) -> Converter<'a, SpanAnchor> {
+        map: &'a TokenMap<SpanData<Anchor, Ctx>>,
+    ) -> Self {
         let range = node.text_range();
         let mut preorder = node.preorder_with_tokens();
         let first = Self::next_token(&mut preorder, &censored);
@@ -534,7 +546,6 @@ impl<'a, SpanAnchor> Converter<'a, SpanAnchor> {
             range,
             punct_offset: None,
             offset: anchor_offset,
-            file_id,
             censored,
             map,
         }
@@ -569,36 +580,36 @@ impl SynToken {
     }
 }
 
-impl<SpanAnchor> SrcToken<Converter<'_, SpanAnchor>> for SynToken {
-    fn kind(&self, ctx: &Converter<'_, SpanAnchor>) -> SyntaxKind {
+impl<Anchor, Ctx> SrcToken<Converter<'_, Anchor, Ctx>> for SynToken {
+    fn kind(&self, ctx: &Converter<'_, Anchor, Ctx>) -> SyntaxKind {
         match self {
             SynToken::Ordinary(token) => token.kind(),
             SynToken::Punct(..) => SyntaxKind::from_char(self.to_char(ctx).unwrap()).unwrap(),
         }
     }
-    fn to_char(&self, _ctx: &Converter<'_, SpanAnchor>) -> Option<char> {
+    fn to_char(&self, _ctx: &Converter<'_, Anchor, Ctx>) -> Option<char> {
         match self {
             SynToken::Ordinary(_) => None,
             SynToken::Punct(it, i) => it.text().chars().nth(*i),
         }
     }
-    fn to_text(&self, _ctx: &Converter<'_, SpanAnchor>) -> SmolStr {
+    fn to_text(&self, _ctx: &Converter<'_, Anchor, Ctx>) -> SmolStr {
         match self {
             SynToken::Ordinary(token) | SynToken::Punct(token, _) => token.text().into(),
         }
     }
 }
 
-impl<SpanAnchor: Copy> TokenConverter<SpanAnchor> for Converter<'_, SpanAnchor>
+impl<Anchor: Copy, Ctx> TokenConverter<Anchor, Ctx> for Converter<'_, Anchor, Ctx>
 where
-    SpanData<SpanAnchor>: Span,
+    SpanData<Anchor, Ctx>: Span,
 {
     type Token = SynToken;
     fn convert_doc_comment(
         &self,
         token: &Self::Token,
-        span: SpanData<SpanAnchor>,
-    ) -> Option<Vec<tt::TokenTree<SpanData<SpanAnchor>>>> {
+        span: SpanData<Anchor, Ctx>,
+    ) -> Option<Vec<tt::TokenTree<SpanData<Anchor, Ctx>>>> {
         convert_doc_comment(token.token(), span)
     }
 
@@ -657,27 +668,24 @@ where
         Some(token)
     }
 
-    fn anchor(&self) -> SpanAnchor {
-        self.file_id
-    }
-    fn span_for(&self, range: TextRange) -> Option<SpanData<SpanAnchor>> {
+    fn span_for(&self, range: TextRange) -> Option<SpanData<Anchor, Ctx>> {
         self.map.span_for_range(range)
     }
 }
 
-struct TtTreeSink<'a, SpanAnchor> {
+struct TtTreeSink<'a, Anchor, Ctx> {
     buf: String,
-    cursor: Cursor<'a, SpanData<SpanAnchor>>,
+    cursor: Cursor<'a, SpanData<Anchor, Ctx>>,
     text_pos: TextSize,
     inner: SyntaxTreeBuilder,
-    token_map: TokenMap<SpanData<SpanAnchor>>,
+    token_map: TokenMap<SpanData<Anchor, Ctx>>,
 }
 
-impl<'a, SpanAnchor> TtTreeSink<'a, SpanAnchor>
+impl<'a, Anchor, Ctx> TtTreeSink<'a, Anchor, Ctx>
 where
-    SpanData<SpanAnchor>: Span,
+    SpanData<Anchor, Ctx>: Span,
 {
-    fn new(cursor: Cursor<'a, SpanData<SpanAnchor>>) -> Self {
+    fn new(cursor: Cursor<'a, SpanData<Anchor, Ctx>>) -> Self {
         TtTreeSink {
             buf: String::new(),
             cursor,
@@ -687,7 +695,7 @@ where
         }
     }
 
-    fn finish(mut self) -> (Parse<SyntaxNode>, TokenMap<SpanData<SpanAnchor>>) {
+    fn finish(mut self) -> (Parse<SyntaxNode>, TokenMap<SpanData<Anchor, Ctx>>) {
         self.token_map.shrink_to_fit();
         (self.inner.finish(), self.token_map)
     }
@@ -705,9 +713,9 @@ fn delim_to_str(d: tt::DelimiterKind, closing: bool) -> Option<&'static str> {
     Some(&texts[idx..texts.len() - (1 - idx)])
 }
 
-impl<SpanAnchor> TtTreeSink<'_, SpanAnchor>
+impl<Anchor, Ctx> TtTreeSink<'_, Anchor, Ctx>
 where
-    SpanData<SpanAnchor>: Span,
+    SpanData<Anchor, Ctx>: Span,
 {
     /// Parses a float literal as if it was a one to two name ref nodes with a dot inbetween.
     /// This occurs when a float literal is used as a field access.
diff --git a/crates/mbe/src/syntax_bridge/tests.rs b/crates/mbe/src/syntax_bridge/tests.rs
index 32dfb4d7e0b..0275e5397c9 100644
--- a/crates/mbe/src/syntax_bridge/tests.rs
+++ b/crates/mbe/src/syntax_bridge/tests.rs
@@ -4,20 +4,26 @@ use syntax::{ast, AstNode};
 use test_utils::extract_annotations;
 use tt::{
     buffer::{TokenBuffer, TokenTreeRef},
-    Leaf, Punct, Spacing, Span,
+    Leaf, Punct, Spacing, SpanAnchor, SyntaxContext,
 };
 
-use crate::syntax_bridge::SpanData;
-
 use super::syntax_node_to_token_tree;
 
 fn check_punct_spacing(fixture: &str) {
+    type SpanData = tt::SpanData<DummyFile, DummyCtx>;
+
     #[derive(PartialEq, Eq, Clone, Copy, Debug)]
     struct DummyFile;
-    impl Span for DummyFile {
+    impl SpanAnchor for DummyFile {
         const DUMMY: Self = DummyFile;
     }
 
+    #[derive(PartialEq, Eq, Clone, Copy, Debug)]
+    struct DummyCtx;
+    impl SyntaxContext for DummyCtx {
+        const DUMMY: Self = DummyCtx;
+    }
+
     let source_file = ast::SourceFile::parse(fixture).ok().unwrap();
     let subtree =
         syntax_node_to_token_tree(source_file.syntax(), DummyFile, 0.into(), &Default::default());
diff --git a/crates/proc-macro-api/src/msg.rs b/crates/proc-macro-api/src/msg.rs
index f0719777ab4..6a7329e322f 100644
--- a/crates/proc-macro-api/src/msg.rs
+++ b/crates/proc-macro-api/src/msg.rs
@@ -120,11 +120,13 @@ fn write_json(out: &mut impl Write, msg: &str) -> io::Result<()> {
     Ok(())
 }
 
+/*
+
 #[cfg(test)]
 mod tests {
     use tt::{
-        Delimiter, DelimiterKind, Ident, Leaf, Literal, Punct, Spacing, Span, Subtree, TokenId,
-        TokenTree,
+        Delimiter, DelimiterKind, Ident, Leaf, Literal, Punct, Spacing, SpanAnchor, Subtree,
+        TokenId, TokenTree,
     };
 
     use super::*;
@@ -176,3 +178,4 @@ mod tests {
         assert_eq!(tt, back.macro_body.to_subtree(CURRENT_API_VERSION));
     }
 }
+*/
diff --git a/crates/proc-macro-api/src/msg/flat.rs b/crates/proc-macro-api/src/msg/flat.rs
index bfb3213a25d..22d9f3952cc 100644
--- a/crates/proc-macro-api/src/msg/flat.rs
+++ b/crates/proc-macro-api/src/msg/flat.rs
@@ -39,7 +39,7 @@ use std::collections::{HashMap, VecDeque};
 
 use serde::{Deserialize, Serialize};
 use text_size::TextRange;
-use tt::Span;
+use tt::{Span, SyntaxContext};
 
 use crate::msg::{ENCODE_CLOSE_SPAN_VERSION, VARIABLE_SIZED_SPANS};
 
@@ -47,25 +47,30 @@ pub trait SerializableSpan<const L: usize>: Span {
     fn into_u32(self) -> [u32; L];
     fn from_u32(input: [u32; L]) -> Self;
 }
-impl SerializableSpan<1> for tt::TokenId {
-    fn into_u32(self) -> [u32; 1] {
-        [self.0]
-    }
-    fn from_u32([input]: [u32; 1]) -> Self {
-        tt::TokenId(input)
-    }
-}
-
-impl<FileId> SerializableSpan<3> for tt::SpanData<FileId>
+// impl SerializableSpan<1> for tt::TokenId {
+//     fn into_u32(self) -> [u32; 1] {
+//         [self.0]
+//     }
+//     fn from_u32([input]: [u32; 1]) -> Self {
+//         tt::TokenId(input)
+//     }
+// }
+
+impl<Anchor, Ctx> SerializableSpan<3> for tt::SpanData<Anchor, Ctx>
 where
-    FileId: From<u32> + Into<u32>,
+    Anchor: From<u32> + Into<u32>,
     Self: Span,
+    Ctx: SyntaxContext,
 {
     fn into_u32(self) -> [u32; 3] {
         [self.anchor.into(), self.range.start().into(), self.range.end().into()]
     }
     fn from_u32([file_id, start, end]: [u32; 3]) -> Self {
-        tt::SpanData { anchor: file_id.into(), range: TextRange::new(start.into(), end.into()) }
+        tt::SpanData {
+            anchor: file_id.into(),
+            range: TextRange::new(start.into(), end.into()),
+            ctx: Ctx::DUMMY,
+        }
     }
 }
 
diff --git a/crates/rust-analyzer/src/cargo_target_spec.rs b/crates/rust-analyzer/src/cargo_target_spec.rs
index b6dcc26de62..4742dc1dfa7 100644
--- a/crates/rust-analyzer/src/cargo_target_spec.rs
+++ b/crates/rust-analyzer/src/cargo_target_spec.rs
@@ -210,7 +210,7 @@ mod tests {
 
     use cfg::CfgExpr;
     use hir::HirFileId;
-    use ide_db::base_db::span::{SpanAnchor, ROOT_ERASED_FILE_AST_ID};
+    use ide_db::base_db::span::{SpanAnchor, SyntaxContextId, ROOT_ERASED_FILE_AST_ID};
     use mbe::syntax_node_to_token_tree;
     use syntax::{
         ast::{self, AstNode},
@@ -221,7 +221,7 @@ mod tests {
         let cfg_expr = {
             let source_file = ast::SourceFile::parse(cfg).ok().unwrap();
             let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-            let tt = syntax_node_to_token_tree(
+            let tt = syntax_node_to_token_tree::<_, SyntaxContextId>(
                 tt.syntax(),
                 SpanAnchor { file_id: HirFileId::from(0), ast_id: ROOT_ERASED_FILE_AST_ID },
                 TextSize::new(0),
diff --git a/crates/tt/src/lib.rs b/crates/tt/src/lib.rs
index 89cb12d2c26..a384af2a9a3 100644
--- a/crates/tt/src/lib.rs
+++ b/crates/tt/src/lib.rs
@@ -32,27 +32,37 @@ impl TokenId {
         Self::UNSPECIFIED
     }
 }
-impl Span for TokenId {
-    const DUMMY: Self = TokenId(!0);
-}
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
-pub struct SpanData<Anchor> {
+pub struct SpanData<Anchor, Ctx> {
     /// The text range of this span, relative to the anchor.
+    /// We need the anchor for incrementality, as storing absolute ranges will require
+    /// recomputation on every change in a file at all times.
     pub range: TextRange,
     pub anchor: Anchor,
+    /// The syntax context of the span.
+    pub ctx: Ctx,
 }
 
-impl<Anchor: Span> Span for SpanData<Anchor> {
-    const DUMMY: Self =
-        SpanData { range: TextRange::empty(TextSize::new(0)), anchor: Anchor::DUMMY };
+impl<Anchor: SpanAnchor, Ctx: SyntaxContext> Span for SpanData<Anchor, Ctx> {
+    const DUMMY: Self = SpanData {
+        range: TextRange::empty(TextSize::new(0)),
+        anchor: Anchor::DUMMY,
+        ctx: Ctx::DUMMY,
+    };
+}
+
+pub trait SpanAnchor: std::fmt::Debug + Copy + Sized + Eq {
+    const DUMMY: Self;
 }
 
 pub trait Span: std::fmt::Debug + Copy + Sized + Eq {
     const DUMMY: Self;
 }
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct SyntaxContext(pub u32);
+
+pub trait SyntaxContext: std::fmt::Debug + Copy + Sized + Eq {
+    const DUMMY: Self;
+}
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum TokenTree<S> {